Female reproductive anatomy

3 roles of the female reproductive system

1. produce gametes

2. produce hormones

3. receive, nourish, deliver a developing embryo

How does the female system operate compared to male system

• Male system= constant, continuous spermatogenesis, steady testosterone

• Female system

  • operates cyclically: fluctuating hormones, endometrial remodeling, and monthly prep for pregnancy, whether or not it occurs

• same HPG axis—but female version adds positive feedback (LH surge)

  • FSH→ support cells

  • LH→ hormone-producing cells

• In the ovary, granulosa cells also convert androgens→ estrogen

Female Internal genitalia

• Ovaries

• Uterine tubes(oviducts/ fallopian tubes)

• Uterus

• Vagina

External genitalia

• Vulva

  • (mons pubis)

  • Labia

  • Clitoris

  • Vestibular glands

Ovaries

• Paired organs flanking the uterus

• almond-shaped(2X size of an almond)

• aka gamete factory

Function of ovaries

produce oocytes (gametes) AND secrete estrogen/progesterone (endocrine) — dual function, analogous to the testis

3 supporting ligaments of the ovaries

1. Ovarian ligament

2. Suspensory ligament

3. Mesovarium

Ovarian ligament

• Medially attaches ovary to uterus

• Short

Suspensory ligament

• Laterally attaches ovary to pelvic wall

• Contains ovarian blood vessels and nerves

Mesovarium

• Attaches ovary to broad ligament

• Part of the broad ligament

• suspends ovary

• -salpinx= fallopian tube

Surface epithelium layer

• Is the outermost layer of the ovaries

• Consists of simple cuboidal cells

  • AKA ‘germinal epithelium’ even though oocytes DO NOT arise here

Tunica albuginea layer

• Layer beneath surface epithelium

• is a dense fibrous capsule

  • same name as testis covering—homologous structure

Cortex of ovaries

• Outer region layer

• Houses ovarian follicles at various stages of development

Medulla of ovaries

• Inner region layer

• Large blood vessels, nerves, lymphatics

Ovarian follicles

• Follicles are tiny sac-like structures in the cortex, each containing:

  • An oocyte (immature egg)

  • One or more layers of surrounding support cells

6 stages of follicle development

1. Primordial follicle

2. Primary follicle

3. Secondary follicle

4. Mature (Graafian) follicle

5. Corpus luteum

6. Corpus albicans

Stage 1: Primordial follicle

• Oocyte + single layer of flat follicle cells

• present from birth

Stage 2: Primary follicle

• Oocyte + cuboidal/columnar granulosa cells

• zona pellucida appears

Stage 3:Secondary follicle

• Multiple granulosa cell layers;

• antral spaces forming;

• theca cells developing outside

Stage 4: Mature (Graafian) stage

• Large antrum (fluid-filled cavity); oocyte on stalk (cumulus oophorus)

• ready for ovulation

Stage 5: Corpus luteum

• Post-ovulation remnant

• temporary endocrine structure producing progesterone + estrogen

Stage 6: Corpus albicans

• Scar tissue

• remnant after corpus luteum degenerates

Ovulation

• Each month, typically ONE mature follicle ruptures at the ovary surface → ovulation

• In older females, the ovarian surface is scarred and pitted from decades of ovulation events

Oviducts

• Also called uterine tubes or Fallopian tubes

• 10 cm long; NO direct connection to the ovary (oocyte is released into peritoneal cavity)

• Supported by the mesosalpinx (part of the broad ligament)

3 regions of oviducts

From most lateral to medial

1. Infundibulum

2. Ampulla

3. Isthmus

Infundibulum of the oviducts

• Funnel-shaped opening to peritoneal cavity; fringed with fimbriae (ciliated, fingerlike projections that drape over ovary)

• fringed Fimbriae(ciliated projections) capture oocyte after ovulation

Ampulla of oviducts

• Wide middle region; half of tube length

• Usual site of fertilization

Isthmus of oviducts

• Narrow medial third

• Opens into superolateral wall of uterus

Wall composition of oviducts + their function

• Smooth muscle layer → peristaltic contractions

• Ciliated epithelium → cilia beat toward uterus

• Nonciliated secretory cells → provide nutrients for oocyte and sperm

Oocyte capture and transport

1. During ovulation, fimbriae stiffen and cilia create fluid currents → sweep oocyte into tube

2. Transport toward uterus by: (a) peristaltic contractions of smooth muscle + (b) ciliary beating of epithelial cells

3. Transit time: 3-4 days from ovulation to arrival in uterus

Ectopic (tubal) pregnancy

Fertilized oocyte implants in tube (usually ampulla) instead of uterus → dangerous

tube cannot support growing embryo; usually requires surgical intervention

Pelvic inflammatory disease (PID)

Ascending infection (often STI) → spreads to tubes → scarring → blocked tubes → major cause of infertility

Uterus

• Hollow, thick-walled, muscular organ; size and shape of an inverted pear

• Location: pelvic cavity, anterior to rectum, posterosuperior to bladder

• Position: usually anteverted (tilted forward over bladder); some women have retroverted uterus

4 regions of the uterus

from most superior to inferior

1. Fundus

2. Body

3. Isthmus

4. Cervix

Fundus of the uterus

Rounded superior portion above uterine tube entry points

Body of the uterus

Major portion of the uterus

Isthmus of the uterus

Narrowed region between body and cervix

Cervix of the uterus

• Narrow inferior neck projecting into vagina

• Consists of

  • Internal os: opening from cervix into uterine body

  • External os: opening from cervix into vagina

  • Cervical canal: between the two

  • Cervical glands: secrete thick mucus filling the canal → keeps uterus sterile

  • At mid-cycle (around ovulation): mucus becomes less viscous → permits sperm entry

Cervical cancer

HPV causes 99% of cases; Pap smear screening; HPV vaccination recommended ages 11-12

4 Ligaments that support the uterus

1. Mesometrium

2. Cardinal (transverse cervical ligaments)

3. Uterosacral ligaments

4. Round ligaments

Mesometrium ligament

Lateral support (part of broad ligament)

Cardinal (transverse cervical) ligaments

Cervix/upper vagina → lateral pelvic walls (strongest support)

Uterosacral ligaments

Cervix → sacrum (posteriorly)

Round ligaments

Uterus → anterior body wall (through inguinal canals to labia majora)

Peritoneal pouches

• vesicouterine (bladder-uterus) and rectouterine (Douglas, rectum-uterus)

• Primary support actually from pelvic diaphragm and muscles of deep perineal space

Uterine prolapse

damage to pelvic floor (e.g., childbirth) → uterus descends; cervix may protrude through vagina

3 layers of uterine wall

1. Perimetrium

2. Myometrium

3. Endometrium

Perimetrium layer of uterine wall

Outermost serous layer (visceral peritoneum) — incomplete

A structural covering

Myometrium

• Thick middle layer; interlacing bundles of smooth muscle

• what contracts during pregnancy and sometimes during menstruation

Endometrium

• Inner mucosal lining; simple columnar epithelium + thick lamina propria with uterine glands

2 strata of the endometrium

1. Stratum Functionalis

2. Stratum Basalis

Functionalis

• Superficial strata and is the disposable layer

• Undergoes cyclic changes; proliferates under estrogen; secretory under progesterone; shed during menstruation

• Vascularized by spiral (coiled) arteries

  • degenerate and regenerate each cycle because they spasm

Basalis

• Deep thin strata(permanent, regenerative layer)

• Does NOT shed during menstruation; contains stem cells that regenerate the functionalis after menstruation

• Vascularized by Straight arteries

  • stable, do NOT degenerate because they don’t spasm

Vascular key to menstruation

• Uterine arteries → arcuate arteries (in myometrium) → radial arteries (into endometrium) → branch into:

  • Straight arteries → supply basalis (stable)

  • Spiral arteries → supply functionalis (cycle-dependent)

• When progesterone drops at the end of the cycle → spiral arteries spasm → ischemia → functionalis dies and sloughs off = menstruation

• Straight arteries are unaffected → basalis survives → regeneration begins under rising estrogen

Vagina

• Thin-walled, distensible tube; 8-10 cm long

• Location: between bladder (anterior) and rectum (posterior)

• No glands — lubrication from cervical mucous glands + interstitial fluid seeping across vaginal epithelium

• Acidic pH: epithelial cells store glycogen → shed → metabolized to lactic acid by resident bacteria (Lactobacillus) → protects against infection but hostile to sperm (semen’s alkaline pH buffers this)

• Hymen: incomplete partition of mucosa near vaginal orifice; anatomically variable

• Vaginal fornix: recess where upper vagina surrounds cervix (posterior fornix deepest)

3 functions of the vagina

1. Receives penis and semen during intercourse

2. Passageway for menstrual flow

3. Birth canal

Wall structure of the vagina

1. Adventitia (outer layer)

   • Fibroelastic CT

2. Muscularis (middle layer)

   • Smooth muscle

3. Mucosa (inner layer)

   • Transverse ridges (rugae)

   • Stratified squamous epithelium (friction-resistant)

External genitalia (vulva)

Everything external to the vagina, collectively called the vulva:

• Mons pubis

• Labia majora

• Labia minora

• Vestibule

• Greater vestibular glands

• Clitoris

• Bulbs of the vestibule

• Fourchette

Mons pubis

Fatty mound overlying pubic symphysis; hair-covered after puberty

Labia majora

• Elongated, hair-covered fatty skin folds

• Male homologue= scrotum

Labia minora

• Thin, hair-free skin folds enclosed by labia majora

• Ventral penile skin (penile raphe)

Vestibule

Recess within labia minora; contains urethral orifice + vaginal orifice

Greater vestibular glands

• Flank vaginal opening; secrete lubricating mucus

• Male homologue= bulbourethral glands

Clitoris

• Erectile tissue; only glans exposed; paired corpora cavernosa;

• richly innervated

• Male homologue= penis

• Only the glans is visible externally; the body extends internally

• Contains paired corpora cavernosa (no corpus spongiosum)

• Hooded by prepuce (formed by anterior junction of labia minora)

• Richly innervated; engorges with blood during arousal

Bulbs of the vestibule

Erectile tissue flanking vagina, deep to muscles

Male homologue= corpus spongiosum/ bulb of penis

Fourchette

Ridge where labia minora joins posteriorly

Perineum of vulva

• diamond-shaped region between pubic symphysis, ischial tuberosities, and coccyx.

• Divided into 2 triangles

  • urogenital triangle (anterior): contains external genitalia + urethral opening

  • anal triangle (posterior): contains anal opening

• Same organization as male perineum

Homologues summary

Why does breast size not correlate with milk production

Pre-lactation breast size reflects adipose content, not glandular tissue. Milk production capacity is similar regardless of breast size